On Tue, Feb 12, 2019 at 04:38:04PM +0100, Juan A. Suarez Romero wrote:
> In opt_peel_initial_if optimization, when moving the continue list to
> end of the continue block, before the jump, could happen that the
> continue list itself also ends with a jump.
>
> This would mean that we would have two jump instructions in a row: the
> first one from the continue list and the second one from the contine
> block.
>
> As inserting an instruction after a jump is not allowed (and it does not
> make sense, as it will not be executed), remove the jump from the
> continue block and keep the one from continue list, as it will be
> executed first.
>
> CC: Jason Ekstrand
> ---
> src/compiler/nir/nir_opt_if.c | 21 +++--
> 1 file changed, 19 insertions(+), 2 deletions(-)
Reviewed-by: Caio Marcelo de Oliveira Filho
> diff --git a/src/compiler/nir/nir_opt_if.c b/src/compiler/nir/nir_opt_if.c
> index 932af9e37ab..a011401b3b4 100644
> --- a/src/compiler/nir/nir_opt_if.c
> +++ b/src/compiler/nir/nir_opt_if.c
> @@ -241,12 +241,29 @@ opt_peel_loop_initial_if(nir_loop *loop)
> nir_cf_reinsert(,
> nir_after_block_before_jump(find_continue_block(loop)));
>
> + bool continue_list_jumps =
> + nir_block_ends_in_jump(exec_node_data(nir_block,
> +
> exec_list_get_tail(continue_list),
> +cf_node.node));
> +
> nir_cf_extract(, nir_before_cf_list(continue_list),
> nir_after_cf_list(continue_list));
>
> - /* Get continue block again as the previous reinsert might have removed
> the block. */
> + /* Get continue block again as the previous reinsert might have removed
> the
> +* block. Also, if both the continue list and the continue block ends in
> +* jump instructions, removes the jump from the later, as it will not be
"latter"
> +* executed if we insert the continue list before it */
"...before it."
> +
> + nir_block *continue_block = find_continue_block(loop);
> +
> + if (continue_list_jumps) {
> + nir_instr *last_instr = nir_block_last_instr(continue_block);
> + if (last_instr && last_instr->type == nir_instr_type_jump)
> + nir_instr_remove(last_instr);
> + }
> +
> nir_cf_reinsert(,
> - nir_after_block_before_jump(find_continue_block(loop)));
> + nir_after_block_before_jump(continue_block));
>
> nir_cf_node_remove(>cf_node);
>
> --
> 2.20.1
>
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Caio
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